×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Appendix 13 examples - differences with rules?

Appendix 13 examples - differences with rules?

Appendix 13 examples - differences with rules?

(OP)
Hi,

following my thread "failure mode for criteria 3Sm",
I'm into appendix 13 of ASME VIII div 1.

Following rules of chap. 13-13 (vessel of circular cross section having a single diametral staying member), I'm trying to compare my excel sheet with example 13(i) but I find discrepancies.

The example is for unequal pressures;
I find the same membrane stresses for formulas (6) and (7) (13-17(i)(1).

But as for bending stresses in diametral plate I find a big difference (99975psi<>25020 psi).

It seems the parameter L1 which permits the choice of formula (9) or (10) is the source of this trouble.

For a circular cross section, I thought L1 would be 0.

Does anyone know what value should be assigned to L1? (it seems L1 = Lv gives the good result)

Second point (sorry!); the coefficent c appears in formulas both for shell and plate.
Should it be adapted (c value for shell in shell formula; c value for plate in diametral plate in plate formula?)

yours,

tigny
 

RE: Appendix 13 examples - differences with rules?

tigny, on page 427 for eqns (9) & (10), I wonder if that is a misprint and should read:

Lv <= 2R and

Lv > 2R

rather than L1?

I'm looking at the example 13-17(i), but it still doesn't look quite right, like where did the 4 in the 4R^2 term go?

As for your second question I would say yes, c is per shell or plate, whichever is under consideration.

Code gurus?

Regards,

Mike

RE: Appendix 13 examples - differences with rules?

I agree with SnTMan, the choice between formulae (9) and (10) in 13-13 should be based on Lv, not L1 (L1 has no place in a circular section).
And tigny, your result appears incorrect to me by a factor of 4, you probably used R=12 in, but R=6 in in the example.
And c is simply half the thickness for an unreinforced vessel, and of course you should take the thickness of the element under consideration.

prex

http://www.xcalcs.com
Online tools for structural design

RE: Appendix 13 examples - differences with rules?

(OP)
Thank you SnTMan and prex,

SnTMan, the 12² in example 13-17 is 4*R²; R = 6; it's ok.

tigny

RE: Appendix 13 examples - differences with rules?

tigny, agreed, thanks.

Mike

RE: Appendix 13 examples - differences with rules?

(OP)
btw,

another comment to the chap. 13-13 formulas,

when using I1 and I3 with lentgh units in mm, in equations (3), (8), (9) and (10), don't forget to divide them by 25.4

for example, replace I1 by I1/25.4

yours,

tigny

RE: Appendix 13 examples - differences with rules?

(OP)
Hi,

I'm coming back with chapter 13-13 formula's questioning.

For diametral plate bending stress calculation, formula J1c/I3.[(P1-P2)Lv²] (9), we are stuck with Lv parameter

Since we are talking plate, should'nt be Lp parameter instead? This would be coherent with the use of (4R) in the (10) formula, wouldn't it?

Also, instead of L1 in the tests, shouldn't this be "for Lp =< 2R" instead of "for (Lv) L1  =< 2R"?

If anybody 's got a clue...

RE: Appendix 13 examples - differences with rules?

Can't follow you. Lp is not defined in the code, and Lv has its place in those formulae. These tell you to take the shorter span (length of vessel or vessel diameter) to calculate the bending stress in the diametral plate. Didn't check the formula in detail, but I guess it comes from supported rectangular plate analysis.

prex

http://www.xcalcs.com
Online tools for structural design

RE: Appendix 13 examples - differences with rules?

Hello tigny,

It is very interesting your post and I have a new one.

Can we use UG-34 instead of Ap. 13 for calculation of rectangular vessel like headers of aerorrefrigerants?
What do you think?

Please tigny, is it possible to obtain a copy of your excel sheet you are refering above?.

Best regards.
lopezon

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources